This invention relates to a rust converting and rust inhibiting composition, and more particularly, to a primer composition in the form of an aqueous suspension or aqueous emulsion, which is capable of lifting rust from steel and providing the steel with a corrosion resistant surface.
Removal and prevention of corrosion, particularly rust on steel surfaces, continue to be serious problems. At the present time, to provide corroded metal with a corrosion resistant surface, it is necessary for the metal to be cleaned by mechanical and/or chemical means before application of the primer, otherwise the corrosion continues. Further, available rust inhibiting primers have serious disadvantages.
A rust inhibiting primer composed of red lead and iron oxide, as well as a rust inhibiting primer having a fish oil base are well known. However, these primers are not adequate to protect steel from corrosion, particularly when the steel is subjected to relatively severe conditiions.
According to British Pat. No. 915,512, a nonaqueous primer with rust inhibiting properties is obtained by means of a phosphate of calcium or zinc as the rust inhibitor.
A protective coating composition is disclosed in U.S. Pat. No. 3,249,447 which contains a siccative organic coating composition and a polyvalent metal of a di-(aromatic)phosphinate.
In U.S. Pat. No. 4,064,084 a corrosion inhibiting poly(arylene sulfide) coating has been disclosed. This coating must be heated to a temperature of 500.degree.-900.degree. F. to effect a cure, which is an obvious disadvantage.
According to U.S. Pat. No. 4,086,182, a composition which contains a synthetic binding agent and a complexing agent for iron, which is a polymeric esterification product of an aromatic oxycarboxylic acid containing phenolic groups, is capable of converting a surface film of an oxide on iron or steel and to provide a corrosion resistant film. However, the resultant film is deep black in color and moreover, must be removed prior to the application of another coating, since it does not adhere to other paints.
An anticorrosive pigment is disclosed in U.S. Pat. No. 4,211,565 which is obtained by calcining 30 to 70 mol percent of magnesium, calcium and/or zinc oxide, 70 to 30 mol percent of iron oxide and up to 20 mol percent of chromium oxide at a temperature of 200.degree. to 900.degree. C.
An inexpensive, efficient and effective composition which both removes or converts active corrosion to the passive form and provides a protective film which inhibits further corrosion, even under severe conditions, and which is also compatible with other paints has not been disclosed up to the present time.